Blackberry in Zone 9B — Desert Southwest

Blackberries offer a taste of summer sweetness that's incredibly rewarding in our Desert Southwest gardens. Imagine fresh blackberry cobblers or jams made with berries you've grown yourself, a true treat after our long, hot summers. Plus, blackberries are surprisingly versatile, thriving in containers or as part of a productive edible landscape.

Sure, our extreme heat and alkaline soil present challenges, but with proper timing and care, you can absolutely grow blackberries here. Our long 313-day growing season gives you a decent window of opportunity, especially if you focus on getting them established during the cooler months.

Transplant your blackberry bushes outdoors from early February through early March. This allows them to settle in before our extreme heat kicks in. Before transplanting, harden off your bare-root canes or potted plants by gradually exposing them to outdoor conditions for about a week.

Space your plants 3-5 feet apart to give them plenty of room to grow. Keep an eye on the weather forecast around transplant time; a late cold snap can stress young plants, so be ready to cover them if needed.

Blackberries need consistent moisture, especially when they're fruiting. While they're more drought-tolerant than raspberries once established, don't let them completely dry out, especially during our hot, arid summers. You'll need to be vigilant about watering.

During the active growing season (spring and fall), aim for about 1-2 inches of water per week, depending on rainfall. Use the "finger test" – stick your finger about 2 inches into the soil; if it feels dry, it's time to water. Water deeply at the base of the plant to encourage strong root growth and avoid wetting the foliage, which can lead to fungal issues in our occasional monsoon humidity.

Watch for signs of underwatering, like wilting leaves and dry, brittle canes. Overwatering can cause root rot, so ensure good drainage and look for yellowing leaves. Applying a thick layer of mulch around the base of your blackberry plants helps retain moisture in our dry climate.

Blackberries are vining plants and need a strong trellis system to support their vigorous growth. A sturdy wire trellis or fence works best, allowing you to train the canes for maximum sunlight exposure and easier harvesting. Install your trellis before or at the time of planting to avoid disturbing the roots later.

Train the canes along the trellis wires, spacing them evenly for good air circulation. Thornless varieties are much easier to manage on a trellis, saving you from painful scratches. Regular training will keep your blackberry patch tidy and productive.

Blackberries benefit from minimal but strategic pruning. After harvest, remove the spent floricanes (the canes that produced fruit) down to the ground. These canes won't produce again, and removing them improves air circulation and reduces disease risk.

During the growing season, tip-prune new primocanes (the current year's growth) when they reach about 4-5 feet tall. This encourages branching, which leads to more fruit production the following year. As our first frost approaches around mid- December, stop pruning and let the plants harden off for winter.

Expect your first blackberry harvest from early April through late May, depending on the variety and our spring temperatures. The berries are ready to pick when they are fully black, not dark red. A ripe blackberry should pull off the cane easily without squeezing.

The surface of a ripe blackberry will be dull, not shiny, indicating full ripeness. Harvest regularly to encourage continued production. Blackberries don't ripen off the vine, so only pick the fully ripe ones. Keep harvesting until our first frost (mid- December) signals the end of the season.

Here are some common problems to watch out for with blackberries in the Desert Southwest:

Spotted Wing Drosophila

• What it looks like: Tiny flies lay eggs in ripening fruit, causing soft spots and rot. You might see small larvae inside the berries.
• What causes it: This pest thrives in humid conditions. While our desert is arid, monsoon season can create temporary favorable conditions.
• How to fix/prevent it: Use netting to exclude the flies, especially during fruit ripening. Remove and destroy any infested fruit promptly.

Cane Blight

• What it looks like: Brown or purple lesions appear on the canes, often near pruning cuts or injuries. The affected canes may wilt and die back.
• What causes it: A fungal disease that enters through wounds on the canes, exacerbated by wet conditions.
• How to fix/prevent it: Prune out infected canes below the lesion and dispose of them. Avoid overhead watering and ensure good air circulation.

Orange Rust

• What it looks like: Bright orange pustules appear on the undersides of leaves in spring. Infected canes may be stunted and unproductive.
• What causes it: A systemic fungal disease that infects the entire plant.
• How to fix/prevent it: Remove and destroy infected plants entirely, as there is no cure. Choose disease-resistant varieties.

Japanese Beetles

• What it looks like: Metallic green beetles feed on leaves, leaving behind a lacy skeleton. They can also damage the fruit.
• What causes it: These beetles are attracted to stressed plants.
• How to fix/prevent it: Handpick beetles off the plants in the morning and drop them into soapy water. Use insecticidal soap as a last resort.

Desert Southwest Specific Challenges: Our extreme heat can stress blackberry plants, making them more susceptible to pests and diseases. Sunscald can also be a problem, so provide afternoon shade during the hottest months. The monsoon season can bring humidity that favors fungal diseases, so ensure good air circulation and avoid overhead watering. Alkaline soil can also affect nutrient uptake, so amend your soil with compost and consider using fertilizers formulated for acid-loving plants.

Good companions for blackberries in the Desert Southwest include:

• Tansy: Deters pests like Japanese beetles with its strong scent.
• Garlic: Acts as a natural fungicide and insect repellent, protecting against common blackberry issues.
• Green Beans: Fix nitrogen in the soil, benefiting blackberry growth, and don't compete for the same nutrients.
• Mint: Attracts beneficial insects and pollinators, but keep it contained to prevent it from spreading aggressively.

Avoid planting blackberries near:

• Tomatoes, Peppers, and Potatoes: These plants are susceptible to verticillium wilt, a soilborne disease that can also affect blackberries. They also compete for similar nutrients.